Single voice print issue

## Fixes
- Fixed a bug when generating a PDF with voice parts through the Menu ```"File > Generate PDF... > Parts > Generate..."```. All the notes of a voice would be squeezed into one line.
- Fixed a bug when viewing the voice parts window through the Menu ```"View > View parts
    window"```. All the notes of a voice would be squeezed into one line, with some of the variant versions.

### Example:
![image](https://cloud.githubusercontent.com/assets/3244729/3239989/3f69ca6e-f11a-11e3-9632-6d9090775ce0.png)

## Enhancements
- When generating a PDF with voice parts, each voice is now printed on a separate page. 
- Changed the page size of the generated PDF to A4 Portrait.